link: Non-Relational Databases

Wide-Column Databases

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Each piece of data is stored in a table-like structure. Wide column databases are most similar to Relational Databases. The data can be unstructured though, and doesn’t need to have a rigid schema. Wide-column databases are almost like a hybrid of a key-value Database and a relational Database. Each piece of data is stored with a unique key that points to a series of column types that can vary from row to row. 

This type of database is commonly used when there is a large number of data points with different column types. For example, records from an IoT device will have frequent entries but potentially different data types. Cassandra and HBase are popular options for wide column databases.